Party line printing telegraph system



G. J- KNANDEL., Er AL 2,306,734

PARTY LINE PRINTING `TELEGRPH SYSTEM Filed Feb. 2l, 1940 2 Sheets-Sheet 1 ...25 Q mbv.

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.momma I GAL/(NANDEL ATTORNEY De@ 29, 1942- G. J. KNANDEL l-:T AL "2,306,734

PARTY LINE PRINTING TELEGRAPH SYSTEM Filed Feb. 2l, 1940 2 SheeLS-Sheef 2 22,/ RECT/F/ER POL AR/ZED AAA Hl. l U

y 'su u) 2 f-G JKNAND'L /NVENTORS f G ALOCKE ATTORNE Y Patented Dec. 29, 1942 NETE STATES PARTY LINE PRINTING TELEGRAPH SYSTEM George J. Knandel, Glen Rock, N. J., and George A. Locke, Glenwood Landing, N. Y., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application February 2.1, 1940, Serial No. 319,992

' 10 claims.

This invention relates to a communication system for transmitting signaling impulses over telegraph lines or channels and more particularly to a telegraph system for connecting an outlying telegraph subscribers station to a central switching oce over va telegraph line or channel.

An object or the invention is to lock out 'or prevent a subscribers station from using a line when another Subscribers station is operatively connected to the same line.

Another object is to utilize a telegraph line of the trunk or repeatered type as a means whereby there may be connected one of a plurality of subscribers stations to a central omce,

' thereby giving the subscribers a party line service over a particular trunk.

Another object of the invention is to permit one only of such plurality of subscribers stations to be connected to a line extending to a repeater station which in turn is connected to a telegraph exchange ofce.

Another object is to provide a plurality of sub scribers with teletypewriter switching service over one line by improved means.

According to an embodiment of the present invention, two or more subscribers telegraph stations may be connected over individual lines to relay contacts of a switching arrangement located in a switching center at a local telephone central oice or other convenient place, the switching arrangement being connected to a telegraph line circuit of the long line type that extends through one or more repeater stations connected to a distant telegraph exchange oflice. a line circuit which extends from'the repeater 'I'he relay arrangement is controlled either over a line circuit which extends from the repeater station, or from any one of the subscribers stations, depending upon the direction in which the call originates. The relay arrangement at a local telephone central office provides a combination of relay-operated circuits whereby the subscriber at one station of a party line group is prevented from establishing a connection to the exchange oce or to the telegraph circuit terminating at the exchange oiiice when another station of the group is busy.

A feature of the invention is locating the switching equipment at a local telephone central oiice for maintenance purposes.

Another feature is the provision of lock-out relay in the relay arrangement for preventing one subscribers station of a party line group from seizing a line when the line is engaged by another subscribers station of the group.

Another feature is the use at the switching center of a relay arrangement comprising a plurality of relays individual to the outlying subscribers stations of a party line group, each of the relays being operable through a rectifier and controlled by the source of message signals at its associated subscribers station.

Another feature is the use of each of the relays individual to the outlying subscribers stations of a party line group for connecting the associated subscribers station to'the line and locking out other subscribers station of the group whenY the associated station is connected to the line.

AAnother feature resides in the relay arrangement at the switching center, whereby as many party line vsubscribers stations may be connected as is possible to add a relay for each subscribers station and an armature to each of the other relays for every subscribers station that may be connected. f Y

The invention will now be described with respect to the accompanying drawings which illustrate the telegraph exchange system in which anembodiment of the invention may be satisfactorily adapted. The drawings are arranged into two figures:

Fig. 1 shows a distant telegraph exchange cffice connected on one side to a single telegraph subscribers station and on the other side to a toll line extension circuit extending toa repeater at a distant point and a line outgoing to a telephone central office.

Fig. 2 shows a switching arrangement at a local telephone central office whereat the line stations. l

Referring to Fig. 1 of the drawings, a subscribers teletypewriter set I Il I at station A comprising transmitting contacts |02 and printing magnet |03 of a teletypewriter is connected over a line |04 which terminates in jack |05 of the subscribers line circuit equipment at the teletypewriter exchange cnice. The equipmentat the subscribers station A and at the termination of the line may be similar to that shown in Fig. 5 of U. S. Patent 2,143,000 granted to W. W. Cramer et al. on January 10, 1939. Line IM may be one of a plurality, as shown terminating at the switchboard at the teletypewriter exchange oice.

By means of the operators cord circuit |06,

the operators position circuit |01 and jack |08,

subscribers line |04 may be extended over a toll line extension circuit, the toll line extension circuit including jack |08 together with the terminating equipment adjacent thereto, repeater |09 and toll line ||0. The repeater |09 may be located at a point distant from the exchange oiiice. The operators cord circuit and the operators position circuit |01 may be similar to those shown in Figs. 3 and 4, respectively, of U. S. Patent 2,143,000, supra. The terminating equipment connected to jack |08 at the exchange oice may be similar to Fig. 8 of U. S. Patent 2,143,000, supra. The repeater |09 may be similar to the left side of Fig. '1 of U. S. Patent 2,143,000, supra.

The toll line |0 terminates at the lower armature of relay which is normally in engagement with its back contact. The toll line ||0 is extended over the lower armature and back contact of relay 20|, conductor 202, lower armature and back contact of relay 203, conductor 204, lower armature and back contact of relay 205, through the winding of alternating current relay 206, condenser 201, to ground. Relays 20|, 203 and 205 are respectively associated with outlying subscribers stations X, Y and Z.

The ringing current generally applied at the switchboard at the distant teletypewriter exchange oice when a connection is established operates the alternating current relay 200. Re-

lay 206 upon operating closes an operating circuit for relay 208. Relay 208 operates and thereby closes over its armatures and their respective contacts three circuits which connect ringing generator 209 and lamp 2|0 to the subscribers stations X, Y and Z, one of said circuits extending over conductors 2 and 2 l2, another of said circuits extending over conductors 2|3 and 2|4 and the third extending over conductors 2|5 and 2|6. Code ringing, which is well known in the telephone art, is employed, that is, one pulse of ringing current is transmitted to call the subscriber at station X, two pulses to call the subscriber at station Y and three pulses to call the subscriber at station Z. The equipment at stations X, Y and Z are identical. A description of the equipment at station X will suce for a description of that at stations Y and Z.

Relays 206 and 208 successively respond to the ringing current transmitted from the switchboard at the distant teletypewriter exchange oice and relay 208, in turn, supplies ringing current locally to the three subscribers stations X, Y and Z. Assume that one pulse only of the ringing current is received. The subscriber at station X answers by turning on power switch 2|1. The operation of switch 2|1 closes a circuit extending from source 2 I8 of alternating current, conductor 2|9, left-hand spring member and contact of switch 2|1, conductor 220, rectifier 22|, conductor 222, back to source 2|3. Connected in parallel with rectier 22| is teletypewriter motor 223. Another circuit closed by the operation of switch 2 I1 extends from ground 224, source 2| 8, conductor 2|9, left-hand spring member and contact of switch 2|1, conductor 22,0, through the winding of alternating current relay 225 to ground. Motor 223 and relay 225 operate and rectier 22| is energized. Y

Relay 225, upon operating, connects conductor 2 |2 through the subscribers set at station X and thence to the subscribers station teletypewriter. Switch 2 1v upon being operated connects a source of positive and negative current obtained from rectier 22| to a circuit extending over conductor 226, contact and outer upper armature of relay 221, conductor 228, right-hand spring member of switch 2|1, in an operated position, control conductor 229, through the switching center whereat the circuit extends through the outer upper armature and back contact of relay 205, outer upper armature and back contact of relay 203, rectier 230, through the winding of relay 20| to ground. The source of positive and negative currents obtained from rectifier 22| will be applied to relay 20| during the time that station X is in use, but will be negative when the subscribers set is in the marking condition and positive when the subscribers set is in spacing condition. Either polarity applied to the control conductor 229 will hold relay 20|, which is associated with subscribers station X, operated as long as the station is in use. Relay 20| upon operating will at its lower armature and back contact disconnect the alternating current relay 206 from the toll line ||0 and toll line ||0 will be extended over conductor 2|2 to the subscribers set at station X. Transmission to and from station X may now take place in the normal manner.

Relay 20|, upon operating, will make the extensions through stations Y and Z busy by connecting grounded battery 23| to two parallel paths being respectively connected to the outer, upper and the inner, upper armatures of relay 20|. These paths respectively extend over conductors 232 and 233 to stations Y and Z shown in diagrammatic form, conductors 232 and 233 being the control conductors for stations Y and Z.

For the purpose of illustration assume that grounded battery is connected to the control conductor 229 whose termination at station X is shown in detail. It will be further assumed that the power switch 2|1 is in normal position as shown in the drawing because the corresponding switch at each of stations VY and Z will be in normal positions when station X is operatively connected to the line. Grounded battery in being connected to conductor 229, is applied to a circuit extending over the right-hand spring member of switch. 2|1 in normal position, conductor 234, through the winding of busy relay 235 to ground. Busy relay 235 operates and thereby closes a cirn cuit extending from source 2|8 of alternating current, conductor 222, armature and contact of relay 235, through the winding of alternating current relay 221,`conductor 2|9 to source 2|8 Relay 221 operates. Accordingly when station X is operatively connected to line ||0, as hereinbefore described, the busy relay corresponding to relay 235 at station X, at each of stations Y and Z, will operate'. The busy relays, being operated, respectively close circuits for operating their associated alternating current relays corresponding to relayV 221. The operation of these alternating current relays at stations Y and Z will result ina busy indication being given by their respectively associated lamps, corresponding to lamp 236, if either or both of the subscribers at stations Y and Z attempt to initiate a call while station X is connected to the line ||0.

At the end of the call, power switch 2 |1 is restored to normal thereby deenergizing rectifier 22|, stopping motor 223, releasing relay 225, and disconnecting the source of alternate positive and negative message signals that was received over conductor 226 andapplied to control conductor 229. ,The disconnection of the source of message signals from control conductor229 causes relay 20| to release. Relay 20| upon releasing restores the busy relays at stations `Y and Z to normal.

Outgoing call from statten X Assume the subscriber atstation X initiates a call if the toll line extension li) is not in use. Power switch 2 I l is operated to connect the source of message signals as applied to conductor 226 and control conductor 229, in series, to operate relay 20| in a manner hereinbefore described. Relay 20| upon being operated connects toll line extension lli) to the subscribers set and thence to the teletypewriter at station X and makes the extensions to the other stations busy in the manner hereinbefore described. If the toll line `extension ll to the switchboard is in use, grounded battery 23'! er 238 depending upon whether station Y or Z is using the line, will be connected to the corresponding control conductor 229 which will result in a busy indication on busy lamp 236 in response to the operation of power switch 2|?.

When a called signal is received at the switchboard at the exchange oiilce from a toll line extension circuit, having three or more stations connected to it, the operator will be unable to distinguish at which of the stations the call originated. It will, therefore, be necessary for the subscriber to transmit signals indicating the name of the calling subscriber as soon as the operator answers. The subscribers teletypewriter circuit as shown at station X is similar to that shown in Fig. l of U. S. Patent 2,143,600, supra, except for modifications to take care of the facility for giving a busy indication and oi furnishing a source of current to operate relays 22|, 203 and 205 at the switching center.

The break, the recall and disconnect features are not ailected by three or more party operations and a recall from any station of a party line group does not provide a means whereby another station ofthe group may take over the circuit, providing a recall key rather than the power switch is employed at each station for recalling. The operation of the recall key opens the message line circuit which does not cause the release of relay 20|, 203 or 205 in the local telephone central oice and therefore the circuit to the subscriber at station X, Y or Z remains locked out.

It is understood that the present invention is not limited to the arrangement shown and that it may be adapted for use in systems having four or more parties connected to the toll line extension circuit. For each additional subscribers station added to the party line, an extra relay such as 20| and an extra rectier such as 239 are required. Also it is necessary to furnish an extra armature on each of the relays such as relays 283|, 203 and 205 and also an extra armature on relay 20S. As many subscribers stations may be added as is practicable to develop multicontact relays or until the line ||i becomes too heavily loaded from a trame standpoint.

What is claimed is:

1. A telegraph system comprising an exchange oice, a switching center, a plurality of outlying stations, a main circuit interconnecting said exchange oiiice and said switching center, a plurality of circuits for respectively connecting said outlying stations to said switching center, a source of current at each of said outlying stations, operable means arranged when operated to impress code signals of alternate positive and negative polarities from said source on one of said plurality of circuits, an electromagnetic means responsive to current' of both positiveV and negative polaritiesfrom said source for maintaining the connection of said one of said plurality oi cir cuits to said main circuit.

2. A telegraph system comprising an exchange oice, a switching center, a plurality of outlying stations, a normally idle main circuit interconnecting said exchange olce and said switching center, a plurality oinormally idle circuits respectively connecting said outlying stations to said switching center, a source of current at each of said outlying stations, operable means arranged when operated to impress code signals of alternate positive and negative polarities from one of said sources on one of said plurality of circuits, an electromagnetic means responsive to the code signals of positive and negative current of its associated source for operatively connecting said one of said plurality of circuits to said main circuit, and means coincidentally operative with the electromagnetic means associated with said one of said plurality of stations for preventing any one of the other of said plurality of circuits from being operatively connected to said main circuit.

3. A telegraph system comprising an exchange oice, a main line from said oce to a switching center, a plurality of subscribers stations having individual lines extending to said switching center and connectable to said main line, a circuit varying device at each of said subscribers stations operable to control the connection of its line to said main line at said switching center, a signal at each subscribers station, and means whereby operation of said circuit varying device at any of said stations actuates its associated signal when any other of said circuit Varying devices has previously been and remains operated.

4. A telegraph system comprising a teletypewriter exchange o'ice, a switching center, a plurality of subscribers teletypewriter stations, a main circuit interconnecting said exchange ofce and said switching center, a plurality of circuits respectively connecting said plurality of subscribers stations to said switching center, a supply source of code signals of positive and negative current at each of saidv subscribers stations,

operable means arranged when operated to impress code signals of positive and negative polarities from its associated one of said sources on its associated one of said plurality of circuits, and a control device responsive to the code signals of positive and negative polarity from said one source for operatively holding connected one of said plurality of subscribers stations to said main circuit and indicating means comprising a signal at each of said plurality of subscribers stations responsive to the operation of one of said operable means for operating said signal at one of said plurality of subscribers stations when one of the other of said plurality of subscribers stations is operatively connected over its associated circuit to said main circuit.

5. A telegraph system according to claim 4 wherein one of said indicating means comprises a pair of electromagnetic devices responsive to the operation of one oi said operable means associated with one of the other of said plurality of subscribers stations for conditioning its associated said signal to operate when its associated said operable means is operated.

6. A telegraph system comprising a teletypewriter exchange oice, a switching center, a plurality of subscribers teletypewriter stations, a main circuit interconnecting said exchange oice and said switching center, a plurality of circuits respectively connecting said plurality of subscribers stations to said switching center, a source of positive and negative current at each of said subscribers stations, operable means arranged when operated to impress code signals of alternate positive and negative polarities of varying duration from one of said sources on one of said plurality of circuits, and means including a rectifier responsive to the signals of both positive and negative polarities from its associated said source for operatively connecting one of saidA plurality of subscribers stations to said main circuit.

7. In a telegraph system comprising a teletypewriter exchange office, a switching center, a. single channel of telegraphic transmission interconnecting said oce and said switching center, switching instrumentalities for normally terminating said channel at said switching center, a plurality of teletypewriter stations normally terminating at said instrumentalities, means in said instrumentalities responsive to current variations incoming over said transmission channel for transmitting current fluctuations to each of said stations, switching means at each of said stations for initiating an operative connection between one of said stations and said transmission channel, said switching means comprising a source of current which may be varied to produce telegraph impulses, means in said switching center responsive to current from said source for completing said operative connection, and operable elements at each of said stations responsive to the operation of said completing means for preventing one of said stations from being operatively connected to the transmission line when another of said stations is operatively connected to said transmission line.

8. In a telegraph system, an arrangement according to claim 7, wherein the means for varying said current is a teletypewriter cooperating therewith sending message signals over the subscribers station circuit connected to said transmission circuit.

9. A telegraph system comprising a main ofce, a switching center geographically remote therefrom, a plurality of outlying stations, a main circuit interconnecting said exchange ofiice and said switching center, a plurality of circuits for respectively connecting said outlying stations to said switching center and thence to said main oce whereby said plurality of outlying stations have ,access to said exchange ofiice through said main circuit, means operable under control of the main ofiice for selectively indicating at any one of said outlying stations a calling condition for said station, instrumentalities operable at the selected indicated station to establish a connection of a circuit individual thereto and extending therebetween and the switching center to said main circuit for telegraphic intercommuncation between said outlying station and said main office, and further instrumentalities operative by current incidental to said transmission to maintain said connection.

l0. A system in accordance with claim 9 having further means whereby a current incidental to said transmission establishes a, busy condition for all other of said outlying stations.

GEORGE J. KNANDEL. GEORGE A. LOCKE. 

